Issues addressed:

1. Tape deck does not play tapes
2. LCD screen damaged
3. How do you remove the radio from the truck?
4. Why would you want to keep the original head unit?

Just bought a Discovery I, and after spending quite some time troubleshooting the radio, I figured I'd make a write-up that might help others.

To get the radio out can be quite an ordeal on the 1997 model year. There's two holes for a screw driver on the face of the radio, and unscrewing those screws will release the radio. I could never figure out what the drive was, but some people have been saying it is some special pentalobe for theft prevention. Most people seem to try various allen wrenches in hopes the screws will break free. In my case the screws just stripped, so I took the handle off a needle file and with a mild strike of a hammer, I drove the tapered square shank of the file into the screw head (forming it's own drive) and the screw came free after twisting the file with an adjustable wrench. The screws are captive, and if they're unscrewing, it likely means they are missing a circlip - if this happens, put force onto the screw towards the front of the truck. Once you free the radio, wiggle it out, and take note of which connectors go where. The top can be pried off, and the face plate can be negotiated off while taking care not to break the plastic clips. Do not re-use the screws if they stripped. I bought some M4x25 socket heads and used a Dremel to reduce the diameter of the tips down to match the OEM screws. Now I can remove my radio with a 3 mm Allen key.

The first problem that sparked the desire to remove the radio was that the tape deck didn't play tapes. Tip: don't try to pry the tape out, once you take apart the tape deck you can manually turn the motor and the mechanized action will return your tape. There's another thread on this, but in short the problem is usually the fact that the belt which came with the tape deck has dissolved into some kind of black goop. This goop is soluble with isopropyl alcohol and can be quickly cleaned up with a toothpick and some paper towel soaked with alcohol. To get to this goop and replace the belt, you need to take apart the radio which is fairly straightforward - pull the dial, face plate and top cover off, then unscrew the 4 Phillips screws holding the tape deck to the chassis. Once you have the tape deck out, flip it over and unscrew 4 more screws - one is longer than the others so note from where it came. Below you can see how the belt should be routed. I used a rubber band and it works, but there are actual belts from Pioneer out there (another thread says it's CNT-1046 or 950FQW8713).


The other problem was the LCD screen. It had become hazy over time.

While I had the radio out, I tried wet-sanding the hazy LCD screen with some 1,000 grit sandpaper. The haziness dissolved, and the LCD didn't work after this. After doing some research online, I found that this was likely the polarizer.

As you can buy polarized film online for cheap, I found some on Amazon for photography ($7). You have to make sure the polarization is at the right angle, otherwise the digits will not display (or may be inverted such that the digits are green and the rest of the screen is black - some people might desire this look). Hold the polarizer in front of the screen and rotate it to see what angle works best (make sure you're holding it with the adhesive backing on the right side). The LCD module can be removed very easily once you have the radio on a desk.

You will need to de-solder 4 feet holding the metal retainer on the back of the LCD's PCB, and then you can disassemble each layer of the LCD. Be sure to keep everything in the right orientation as you go, or take notes. Once I got the LCD out, I carefully sanded off the remaining original polarizer (1,000 grit wet sanding again), being careful not to crack the glass. I then applied the adhesive backed polarization film to the clean surface with a slow rolling motion to prevent air bubbles from forming. It's critical that you trim the polarizer film close to the glass and then sand it totally flush to the edges of the glass - if the polarizer film protrudes even a little, some of the LCD segments will not show up. Once the new film is on, reassembly is the reverse order of disassembly. But you might want to function test the LCD before you solder the metal retainer back on. Be sure to install the face of the radio if you want to test the backlight.


Why all the effort?
For me, it's because I wanted the original look. But tapes are about $1 at thrift stores and you can buy bluetooth receivers with a cassette tape format that connect to your phone, and you can stream whatever you want that way.

This took me about 6 hours of labor, and $7. I hope others will be able to do everything in 2 or 3 hours with these directions.

 

Thanks for the detailed write up and photos

 

Great write-up! Mine has the weather channel function (WB button) , and the CD player under the pass seat (with the cartridge for the CD's) and the CD player doesn't work, haven't tried the cassette player, but the radio and weather work great! I did have to get the code from the dealership. Which I got over the phone after a few calls. I like the look on the dash!

 

If you CD player powers up and provides the 'heartbeat' to the head unit, you can intercept the audio lines from the CD to the head unit and splice in female RCA connectors to the head unit. Then use a Bluetooth dongle. Tap the power to the CD player for the Bluetooth.

Pin 1: left channel ground
Pin 2: left channel positive
Pin 3: right channel ground
Pin 4: right channel positive